Exploring anticancer efficiency of mitochondria-targeted cyclometalated iridium(III) complexes
Graphical abstract
Three iridium(III) complexes [Ir(PPY)2(MPPIP)](PF6) (1) (PPY = 2-phenylpyridine, MPPIP = 2-(4-(4′-methylpiperazin-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), [Ir(BZQ)2(MPPIP)](PF6) (2) (BZQ = benzo[h]quinolone) and [Ir(PIQ)2(MPPIP)](PF6) (3) (PIQ = 1-phenylisoquinolone) were synthesized and characterized. The anticancer activity in vitro and in vivo of the complexes was investigated in detail.
Introduction
Cisplatin as anticancer drugs announced the initiation of a new era for investigating the anticancer activities of metal-based complexes [1]. To date, cisplatin, carboplatin and oxaliplatin as anticancer drugs are commonly used for many cancer treatment [2]. At present, platinum drugs are used in more than 50.0% of chemotherapy treatments [3]. Nevertheless, owing to the several deficiencies, such as intrinsic or acquired resistance and serious side-effect, Therefore, further clinical application of cisplatin has been hindered [4]. These defects have encouraged to search for other metal complexes as potential anticancer drugs. As promising candidates and alternative drugs of cisplatin, the studies on anticancer activities of other metal complexes have received a great attention [[5], [6], [7]]. Among these metal complexes, owing to organometallic iridium(III) complexes having abundant photochemical and photophysical characteristics and cell permeability [8], Ir(III) complexes as anticancer reagents have gained significant prominence [[9], [10], [11], [12], [13], [14], [15], [16]]. Presently, iridium(III) complexes exhibit not only high cytotoxic activity, but also remarkable antitumoral and antimetastatic activities [17,18]. A lot of these Ir(III) complexes target the mitochondria, and lead to mitochondrial dysfunction. Consequently, these complexes bring about apoptosis by a ROS-regulated mitochondrial dysfunction pathway [[19], [20], [21], [22], [23], [24]]. To gain added anticancer properties, we prepared a new ligand MPPIP (MPPIP = 2-(4-(4′-methylpiperazin-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) and Ir(III) polypyridyl complexes: [Ir(N-C)2(MPPIP)](PF6) (N-C = PPY: 2-phenylpyridine, 1; BZQ: benzo[h]quinolone, 2; 1-PIQ: phenylisoquinolone, 3, Scheme 1). Anticancer efficiency of 1, 2 and 3 toward several cancer cell lines was explored through cytotoxicity, intracellular ROS levels, mitochondrial membrane potential, cell colonies formation and apoptosis. The anti-tumor activity in vivo of the complex 3 against xenograft nude model was also evaluated. Furthermore, our findings demonstrated that complexes 1, 2 and 3 trigger apoptosis against A549 cells by a ROS-regulated dysfunction of the mitochondria pathway.
Section snippets
Materials and methods
IrCl3·3H2O was bought from the Kunming Boren Precious Metals Co., Ltd. HeLa (human cervical), A549 (human lung carcinoma), BEL-7402 (human hepatocellular carcinoma), SGC-7901 (human gastric adenocarcinoma) and normal mouse embryonic fibroblast NIH3T3 cells were gained from the cell center of Sen-Yat Sun University (Guangzhou, China). Dimethylsulfoxide, 1,10-phenanthroline, RNAse A, Propidium iodide (PI) and MTT were bought from Beijing HWRK Chemical Co., Ltd. (Beijing, China). NMR spectra were
Chemistry
Synthetic route for MIPIP and its complexes is depicted in Scheme 1. MPPIP was prepared with 4-(4-methylpiperazin-2-yl)benzaldehyde and phenanthroline-5,6-dione using glacial acetic acid as solvent. 1, 2 and 3 were prepared with relative precursor complexes and MPPIP in a mixture of CH2Cl2 and CH3OH. 1-3 were characterized by EA (elemental analysis), 1H, 13C NMR and ESI-MS. In the ESI-MS spectra for 1, 2 and 3, the determined molecular weights are the same as those of calculated molecular
Conclusions
Three iridium(III) complexes: [Ir(PPY)2(MPPIP)](PF6) (1), [Ir(BZQ)2(MPPIP)](PF6) (2) and [Ir(PIQ)2(MPPIP)](PF6) (3) have been successfully prepared and characterized. Cytotoxic activity and cell colonies formation show that 1, 2 and 3 display high capability to prevent to proliferate. Further studies on the cell cycle distribution suggest that 1, 2 and 3 at G0/G1 phase suppress cell growth. Besides, these complexes may augment the levels of intracellular reactive oxygen species and cut down the
Abbreviation
- A549
human lung carcinoma
- adppz
7-aminodipyrido[3,2-a:2′,3′-c]phenazine
- BCA
bicinchoninic acid
- BEL-7402
human hepatocellular
- CCCP
carbonylcyanide-m-chlorophenylhydrazone
- DAPI
2-(4-amidinophenyl)-6-indolecarbamidine dihydrochloride
- DCHF
2′,7′-dichloro-3,6-fluorandiol
- DCHF-DA
2′,7′-dichlorodihydrofluorescein diacetate
- DCF
dichlorofluorescein
- DMSO
dimethylsulfoxide
- EDTA
ethylene diamine tetraacetic acid
- FBS
fetal bovine serum
- HeLa
human cervical cancer
- JC-1
5,5′,6,6′-tetrachloro-1,1′,3,3′-tetrethylbenzimidalylcarbocyanine
Declaration of competing interest
Authors declare no competing interest exists.
Acknowledgements
We are grateful to the National Natural Science Foundation of China (No 21877018) for their financial supports.
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